Handle nested position:sticky elements correctly (compositor)

third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-top-expected.html

Index: third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-top-expected.html
diff --git a/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-top-expected.html b/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-top-expected.html
new file mode 100644
index 0000000000000000000000000000000000000000..03a4030bf7dc9fdc848ee9f7c038a9ad80c43e6e
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-top-expected.html
@@ -0,0 +1,76 @@
+<style>
+body {
+  margin: 0;
+}
+
+.group {
+  display: inline-block;
+  position: relative;
+  width: 250px;
+  height: 350px;
+}
+
+.scroller {
+  overflow: auto;
+  width: 200px;
+  height: 350px;
+  outline: 2px solid black;
+}
+
+.container {
+  width: 200px;
+  height: 700px;
+}
+
+.outerBox {
+  position: relative;
+  background-color: green;
+  width: 200px;
+  height: 200px;
+}
+
+.innerBox {
+  position: relative;
+  background-color: red;
+  width: 200px;
+  height: 100px;
+}
+</style>
+
+<script>
+window.addEventListener('load', function() {
+  for (const scroller of document.querySelectorAll('.scroller')) {
+    scroller.scrollTop = 200;
+  }
+});
+</script>
+
+<div class="group">
+  <div class="scroller">
+    <div class="container">
+      <div class="outerBox" style="top: 250px;">
+        <div class="innerBox" style="top: 0;"></div>
+      </div>
+    </div>
+  </div>
+</div>
+
+<div class="group">
+  <div class="scroller">
+    <div class="container">
+      <div class="outerBox" style="top: 250px;">
+        <div class="innerBox" style="top: 50px;"></div>
+      </div>
+    </div>
+  </div>
+</div>
+
+<div class="group">
+  <div class="scroller">
+    <div class="container">
+      <div class="outerBox" style="top: 250px;">
+        <div class="innerBox" style="top: 100px;"></div>
+      </div>
+    </div>
+  </div>
+</div>